In a circuit substrate that composes a display such as a liquid crystal display and an organic EL display, a microelectronic device for controlling each pixel of the display is disposed, and a circuit that transmits input and output signals of the microelectronic device is formed. Conventionally, in this circuit substrate, the microelectronic device is disposed by producing the device directly on a glass circuit substrate in situ. That is, the microelectronic device such as a thin film transistor (TFT) is formed by laminating an insulation film and a semiconductor film sequentially on the glass circuit substrate using a vacuum technology such as CVD (chemical vapor deposition) and then applying to these deposited films the same steps as those for producing a semiconductor integrated circuit. Such microelectronic devices are formed in the vicinity of each pixel and control on/off and contrasting density of each pixel, to realize an image formation on the display.
In recent years, the displays having a large screen of 40 to 100 inches have been desired and already commercially distributed. However, the method for producing the circuit substrate that requires a multistep process using the aforementioned glass substrate and vacuum technology is a obstacle to reduce cost. For achieving widespread use of the large screen displays, the cost must be reduced. Therefore, there has been sought a method for producing the circuit substrate whereby the cost for producing the large screen display is reduced.
Recently, a new technology has been proposed for addressing to the aforementioned demand for cost reduction of the large screen display (Patent Document 1). In the technology disclosed in this Patent Document 1, a circuit chip produced separately is used as the microelectronic device, and a plastic substrate that is inexpensive and has a light weight is used as the circuit substrate. Applying a printing technology, the circuit chip is disposed on the plastic substrate, and the circuit is produced, which enables production of a large screen display at a low cost.    Patent Document 1: JP 2003-248436-A